mesh intersect

hi there,

i created a mesh and now i want to check it for possible intersections with vectors.

i have a "person's head" and "possible viewpoints" outside of my "built structure"

now i want to check whether or not the person can see the "possible viewpoits".

so i made up vectors from "person's head" to "possible viewpoints". then i intersected these vectors (=rays) with my "built structure" (=mesh). but it seems like i don't get the correct amount of intersecting points (=hits)...

why that?

file attached